Because of cousin Maurice's perceived flamboyant playboy image and his conduct in political and business activities, Édouard considered him to be something of a black sheep. They tolerated each other for the sake of the business but by the middle of the 1930s their differences reached a point where Édouard and cousin Robert decided to force Maurice out of de Rothschild Frères bank. After extensive and bitter negotiations, a buyout was reached through an arbitrator.

Édouard de Rothschild kept a stable of thoroughbreds at the Chantilly Racecourse in Chantilly, Oise and raced horses at racecourses throughout France with great success. Among the major races his horses won were:

During the German occupation of France in World War II, the Nazis seized some of the best racehorses in the country, shipping more than six hundred of them to Germany for racing and/or breeding. Among the horses stolen was Édouard de Rothschild's champion Brantôme who was sent to the German National Stud. The horse was repatriated at the end of the war in 1945 and became a leading sire.

The rise to power of Adolf Hitler's National Socialist party in Germany and the subsequent Anschluss of Austria to Germany saw a wave of Jews, and others the Nazis labeled as "undesirables," seek refuge in France. Most of these people escaped with little more than a suitcase of clothes. In March 1939, Édouard's wife Germaine converted an old house near the Château de Ferrières into a hostel for some 150 of these displaced persons. However, with the onset of World War II and the subsequent German occupation of France in 1940, Édouard de Rothschild and his family themselves chose to flee the country. In 1939, Édouard's son Guy joined the French Army and his daughter Jacqueline escaped with her husband Gregor Piatigorsky to the United States. Before leaving, Édouard de Rothschild tried to hide as much of his valuable art collection as possible, on the grounds of the Haras de Meautry farm and at his Château de Reux. The Nazis confiscated his collection.[2]

With his wife and second daughter Bethsabée, he safely left France and they made their way to Lisbon, Portugal from where they were able to go by plane to New York City. With the Allied liberation of France in 1944, Édouard de Rothschild and his wife returned home,[1] where he died in Paris in 1949 at the age of eighty-one. His son Guy took over as head of the family bank.

On 1 March 1905, Edouard de Rothschild married Germaine Alice Halphen (1884–1975).[1] They had four children, but according to his daughter Jacqueline, neither parent paid much attention to them.[3] Their children were: